JPS6017659Y2 - Cooling water discharge and recovery device for cask internal cooling pipes - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device that safely, reliably, and easily discharges and recovers cooling water from the internal cooling pipe device of a wet cask containing spent nuclear fuel.

Spent nuclear fuel storage casks generate heat due to the decay heat of the nuclear fuel, so they cannot be stored or stored on land or on ships.
During transportation, it is necessary to constantly cool the product, so wet-type casks, that is, casks with a built-in liquid cooling device, are generally used.

The internal cooling system of this wet cask is normally stored connected to an external cooling system that forms a cooling water circulation system for supplying and recovering cooling water, but it is stored in a state where it is connected to an external cooling system that forms a cooling water circulation system for supplying and recovering cooling water. When the cask is to be transferred to a storage facility, the internal cooling system of the cask must be deactivated and both cooling systems must be disconnected.

During this separation, it is necessary to completely drain the cooling water from the internal cooling system of the cask.

If cooling water remains in the internal cooling system,
Cooling water heated to a high temperature by the decay heat of the nuclear fuel leaks out, causing not only a loss of cooling water but also a great danger to workers. When the valve is closed, the pressure inside the internal cooling device increases due to the heating caused by the decay heat, so the pressure difference when the waist valve connected to the external cooling device is opened again gives a sudden pressure mink to the external cooling device, etc. This is because it causes trouble.

For this reason, several measures have been taken to discharge cooling water when the cooling system is disconnected. For example, the cooling piping in the disconnected section is shut off with a valve, and the remaining cooling water in the internal cooling system is forced out using compressed air. A compressed air type discharge device (Japanese Patent Publication No. 53-42143) is used to shut off the piping in the disconnected section with a valve, open the air intake valve at the top of the piping system,
A gravity-type discharge device (Special Publication No. 53-42144) that communicates the internal cooling device with the atmosphere and discharges cooling water by the action of gravity, or a vacuum pump in which the piping in the disconnected section is shut off with a valve. By creating a vacuum in the tank installed in the system, the cooling water in the internal cooling system is
A vacuum-type discharge device (Japanese Patent Publication No. 53-42125) has been proposed in which suction and recovery are carried out into the vacuum tank.

However, the above-mentioned compressed air method not only requires troublesome maintenance and inspection of the compressor in the piping system, but also requires the introduction of high-pressure air by the compressor.
There is a risk of leakage in the piping system, and the gravity method is advantageous in terms of maintenance/inspection, operability, cost, etc.)
This may not be possible depending on the shape of the cask, and in particular, the shape of the cooling piping in the lower half of the cask in the internal cooling system is generally U-shaped, so there is a fatal drawback in that it is not possible to drain the cooling water remaining in that part. has.

Furthermore, with the vacuum method, cooling water is discharged by recovering it in a vacuum tank, so batch operation is inevitable, and in the event of an abnormality, for example, when the cooling water cannot be completely discharged. There are other problems such as slow response time, the need for maintenance of the vacuum pump, relatively complicated operation, poor reliability, and high price.

The present invention provides an improved discharge recovery device for solving the above-mentioned problems regarding the cooling water discharge of the cask internal cooling device. In addition to installing piping, a cooling water recovery tank equipped with an ejector is installed, and when disconnecting the cask internal cooling system piping and external cooling system piping, the cooling water in the external cooling piping and internal cooling pipe in the disconnected section is removed by operating a valve. The first stage is a discharge operation in which a portion of the cooling water is removed by gravity, and then the ejector is operated under the action of atmospheric pressure due to air intake from the air piping, and the cooling water remaining in the internal cooling piping is removed from the collection tank. The second to be collected within
By performing the discharge operation in stages, there is no need to install any mechanically moving parts in the piping system, and cooling can be achieved economically through simple operation, consisting mainly of opening and closing valves, and through continuous operation. This made it possible to achieve complete discharge and recovery of water.

Next, the device of the present invention will be explained in detail according to the drawings.

FIG. 1 is an overall system schematic diagram showing a specific example of the cask cooling water discharge and recovery device according to the present invention.

In the figure, 1 is a cask (a plurality of casks are arranged in parallel as required), and 2 is a cooling water pipe constituting the internal cooling device of the cask.

The cooling water piping generally consists of two lines of piping 2.a and 2.b divided into an upper half and a lower half of the cask, as shown in the figure.
Consists of.

Each of the pipes 2.a and 2.b is connected to the cooling water inlet side,
Removable connectors (e.g. quick connections)
Flexible hoses 4.1a and 4.1 forming the cooling water supply side ends of the external cooling device via 3.1a and 3.1b
b, and on the other hand, on the cooling water outlet side, flexible hoses 4, 2a and 4 at the end of the cooling water return side of the external cooling device are connected via connectors 3, 2a and 3, 2b, which are also detachable.
- Connected to 2b.

Part 5 is a coolant supply/reprocessing unit that is composed of a coolant storage tank 5, an intercooler 6, an intermediate storage tank 7, a coolant feed pump 8, etc., and the coolant is transferred from this to the feed pipe. 9 to the cask internal cooling piping.

The feed pipe 9 includes branch pipes corresponding to the number of installed casks.

The branch pipes 9 and 1 are provided with opening/closing valves 10 for supplying and stopping the cooling liquid, and the end portions of the branch pipes 9 and 1 are arranged in two lines according to the number of cask internal cooling pipes (two lines).
branched into flow paths, each with valves 11・a and 11・b
It is connected to the flexible hoses 4.1a and 4.1b at.

Note that a strainer 22, a coolant thermometer 23, etc. are appropriately installed in the branch pipe 16/1, which is the liquid supply side pipe.

On the other hand, the flexible hoses 4, 2a and 4, 2b on the cooling water outlet side are converged into one cooling water return branch pipe 13, 1 via valves 12, a and 12, b, and communicated with the return pipe 13. are doing.

The branch pipes 13.1 are arranged in the same number as the number of casks,
An opening/closing valve 14 is provided for each of them to allow and stop the flow of cooling water.

The cooling water from Part 5 passes through piping 9, branch piping 9.1, and then to each flexible hose 4.la.

After being introduced into the cask internal piping 2-a and 2-b from 4-1b, each flexible hose 4-2a on the outlet side
From 4.2b, the water passes through the return branch pipe 13.1, passes through the pipe 13, and is returned to Part 5 for circulation.

The cooling pipe is further provided with an air pipe 16 having an air removal head 15 and a cooling liquid recovery tank having an ejector 17.

The air pipe 16 has a number of branch pipes 16, 1 corresponding to the number of casks, and each branch pipe is connected between the valves 10 and 11 of the coolant supply branch pipes 9, 1, respectively.

On the other hand, the recovery tank 18 has a recovery pipe 19 connected between the valve 14 and the valve 12 of the return branch pipe 13.1.

The pipe 19 includes a valve 20 that opens and closes the flow path.

The ejector 17 and the collection tank 18 may be installed for each cask, or one for each unit cask group, where two or more casks form one unit.

A is a compressed air (or steam) source for the ejector 17;
21 is a compressed air pipe, which connects the compressed air source A and the ejector 17.
A valve 24 is provided for supplying and stopping pressurized air during this period.

Note that the pipe 2 that directly connects the air pipe 16 and the recovery tank 18
5 and the valve 26 provided in the pipe are air introduction means for restoring the internal pressure of the collection tank to atmospheric pressure after the ejector is operated, but their role is to
This can be achieved by opening the valve 27 of 6.1, so the provision of the piping 25 is not necessarily necessary.

In this equipment, the external cooling piping system and the cask internal cooling piping system are disconnected from the connectors 3.1a and 3.1a on the cooling water inlet side.
1b and outlet side connectors 3, 2a, and 3, 2b. When disconnecting, the cooling water in the cask internal cooling system piping can be discharged and recovered using the following procedure. Possible: First, the circulating flow of cooling water is stopped by closing the valve 10 of the supply liquid branch piping 9/1 on the cooling water supply side and the valve 14 of the branch piping 13/1 on the return side.

Next, the valve 2 of the recovery pipe 19 leading to the recovery tank 17
By opening valve 0, valve 1 is removed from valve 10.
4 is introduced into the recovery tank 17 via the recovery piping 19 by gravity.

By this first stage recovery operation, the disconnection section of the external cooling piping, that is, from the valve 10 on the liquid supply side to the connector 3/1a
3.1b, the cooling water in the pipes from the connectors 3.2a and 3.2b on the outlet side to the valve 14, and part of the cooling water in the cask internal cooling piping, that is, the cooling water on the upper side of the cask. The cooling water in the pipe 2.a is discharged and recovered.

However, since the piping 2/b on the lower side of the cask, which occupies the majority of the cask internal cooling piping, is U-shaped along the circumferential surface of the cask body as shown in the figure, cooling water remains in this portion.

In order to recover this residual cooling water, a second stage discharge and recovery operation using an ejector is performed following the first stage operation.

In this second stage operation, leave the above-mentioned valves in the open/closed state as they are, but if a pipe 25 connecting the air pipe 16 and the recovery tank 17 is attached, close the valve 26 of the pipe. ), the valve 24 of the compressed air pipe 21 is opened to operate the ejector 17 to create a reduced pressure state in the recovery tank 18, and the valve 27 of the air branch pipe 16.1 is opened.
By opening the valve and introducing air into the pipe in the separation section after the valve 10 and applying atmospheric pressure, the cooling water remaining inside the cask internal cooling pipes 2 and b etc. is removed via the recovery pipe 19. It is introduced into the recovery tank 18.

By the above two-step operation, the cooling water in the separation section from the valve 10 of the liquid supply branch pipe to the valve 14 of the recovery side branch pipe is completely discharged and recovered.

After the recovery of cooling water in the second stage operation is completed, the valve 24 of the compressed air piping is closed to stop the supply of compressed air, and then the cask internal cooling system is separated from the external cooling system.

The procedure for this disconnection operation is to first
By closing the valve 27 of the recovery tank introduction branch pipe 19 to cut off communication with the air pipe, and closing the valve 20 of the recovery tank introduction branch pipe 19, the disconnected section from the valve 10 to the valve 14 is disconnected from the external cooling water pipe system. (In this case, the isolation from the external cooling water piping system may be accomplished by closing the valves 11.a, 11b and 12.a, 12.b), and then each end of the cask internal piping. Flexible hoses 4.1a, 4. with connectors 3.1a, 3.1b and 3.2a, 3.2b. lb and 4.2a,
4. Disconnect from 2b.

The casks thus separated from the external cooling device are transported to other storage facilities by appropriate transportation means.

The coolant recovered in the recovery tank 18 in the above-mentioned coolant discharge and recovery operation is sent to the recovery pipe 28 by opening the valve 29 of the cooling water extraction pipe 28.1 provided at the bottom of the tank.
The water is returned to the 8th section by the feed pump 30, and after undergoing predetermined processing, is recycled and used again as cask cooling water.

The above cooling water discharge and recovery operation was explained using one cask as an example, but the same operation procedure can be used to perform discharge and recovery for each cask when multiple casks are installed side by side. can.

As described above, the device of the present invention is constructed by incorporating a cooling water discharge and recovery piping system equipped with air piping and an ejector into the cooling water piping system, and is operated in two stages by the action of gravity and the depressurizing effect of the ejector. The system is designed to discharge and recover the cooling water in the cask internal cooling piping, and the introduction of atmospheric air from the air piping and the effect of atmospheric pressure play a role in promoting the discharge of cooling water even in the first stage. It has the effect of reducing the load on depressurized discharge by the second stage ejector, and due to the depressurizing effect of the ejector, complete discharge recovery is possible regardless of the shape of the cask internal cooling piping, and its operation is easy. This can be done in continuous operation.

In addition, the main components of this device are only the air piping, ejector, recovery tank, and piping opening/closing valve, and it does not require multiple devices and does not include any mechanically moving parts.
In addition to being easy to inspect and cost-effective, and being able to operate by simply opening and closing valves, the device has excellent reliability and is highly resistant to erroneous operation, such as high pressure Pressure shock to the piping system can be alleviated by taking simple measures such as blowing gas, etc., and it is possible to safely discharge and recover cooling water from the cask internal piping and disconnect the external cooling piping system. It is something.

[Brief explanation of the drawing]

FIG. 1 is an overall system schematic diagram showing a specific example of the device of the present invention. The main symbols in the drawings are as follows. 1: Cask, 2a, 2b: Cask internal cooling piping, 3
・1a, 3・1b, 3・2a, 3・2b=connector, 4”
law 4"lbt 4"2at 4"2b: flexible hose, 9: cooling water supply piping, 16: air piping, 17: ejector, 18: recovery tank, 21: compressed air piping, 28: cooling water recovery piping.

Claims (1)

[Scope of claim for utility model registration] An internal cooling pipe of a wet cask containing spent nuclear fuel,
In a cask cooling system consisting of an external cooling piping system that supplies and collects cooling water to the internal cooling pipe, (a) cooling water supply piping 9 to the cask internal cooling pipe and discharge cooling from the internal cooling pipe; The water return pipe 13 is
Each branch supply pipe 9.1 and branch return pipe 13.1 is provided with the same number of casks 1, and each branch pipe 9.1 and 13.1 has valves 10 and 14 for supplying and stopping cooling water. (b) The branch supply pipes 9 and 1 and the branch return pipes 13 and 1 are further branched according to the number of cooling pipes provided in each cask, and each end thereof is connected to a connector 3. 1a and 3.1b and 3.2a and 3.2b to each end of the water supply side and drainage side of the cask cooling pipe, Branch air piping 16/1 branched according to the number
is connected between the valve 10 of the branch supply pipe 9/1 and the water supply side end of the cask cooling pipe, and the branch air pipe 1
6.1 is equipped with a valve 27 for communicating and shutting off between the atmosphere and the branch supply pipe 19.1, and (
d) A cooling water recovery tank 18 having an ejector 17 is attached, and a compressed air pipe 21 from a compressed air source (4) is connected to the ejector 17 via a valve 24 for supplying and stopping compressed air, In addition, the recovery tank 18 is provided with a pipe 19 that communicates with the recovery tank 18 via a valve 20 from a pipe between the valve 14 of the branch return pipe 13.1 and the end of the cask internal cooling pipe on the drainage side. (e) In addition, there is a cooling water extraction pipe 2 at the bottom of the recovery tank.
8.1 is provided, and the extraction pipe 28.1 is connected to a valve 29.
via a coolant recovery line 28 with a supply pump 30
A cooling water discharge recovery device for a cask internal cooling pipe, connected to a cask internal cooling pipe.